Fix QProperty property interaction with aliases

With this change, an alias of a bindable property is also bindable, and
shares its bindable interface with the target.

Moreover, the logic in QQmlTypeCompiler is adjusted so that a change
handler of an alias uses the bindable interface if possible, instead of
connecting to the alias' change signal. That would never be emitted if
the target is a QProperty without a notify signal.

Alias properties still have a change signal, but those never get
emitted.

Change-Id: I857dfdbe51048a2b604ad632982e7f4adac6b907
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

1 files changed, 3 insertions, 2 deletions

diff --git a/src/qml/qml/qqmltypecompiler.cpp b/src/qml/qml/qqmltypecompiler.cpp
index ca8a24439b..eb3b0e43ac 100644
--- a/src/qml/qml/qqmltypecompiler.cpp
+++ b/src/qml/qml/qqmltypecompiler.cpp
@@ -382,7 +382,8 @@ bool SignalHandlerConverter::convertSignalHandlerExpressionsToFunctionDeclaratio
         QString finalSignalHandlerPropertyName = signalNameCandidate;
         uint flags = QV4::CompiledData::Binding::IsSignalHandlerExpression;
 
-        if (signal) {
+        const bool isPropertyObserver = !signalPropertyData && qPropertyData && qPropertyData->isBindable();
+        if (signal && !(qPropertyData && qPropertyData->isAlias() && isPropertyObserver)) {
             int sigIndex = propertyCache->methodIndexToSignalIndex(signal->coreIndex());
             sigIndex = propertyCache->originalClone(sigIndex);
 
@@ -400,7 +401,7 @@ bool SignalHandlerConverter::convertSignalHandlerExpressionsToFunctionDeclaratio
                 }
                 parameters += param;
             }
-        } else if (!signalPropertyData && qPropertyData && qPropertyData->isBindable()) {
+        } else if (isPropertyObserver) {
             finalSignalHandlerPropertyName = qPropertyName;
             flags = QV4::CompiledData::Binding::IsPropertyObserver;
         } else {